missing when you turn ac on..

K-Farms

K-Farms

F-yea
Joined
Jun 29, 2009
Messages
392
my buddys got an early 07 5.9, when he first got the truck he put a banks iq on it and shorty after got a smarty and ran the two for a wile untill i made him take his banks off. now that its just the smarty whenever you turn the ac on it misses a couple times then comes right out of it back into a smooth idle.. did he screw somthing up in his ecm? should he get it flashed or somthing?...
 
there was issues with the wiring chafing on the side of the compressor..... it would cause ecm issues. mine was chaffed almost into the conductors. may want to check that.
 
yep, on mine the harness was close to the frame rail so i tucked it back.

are you sure its the motor itself missing and not an issue with the compressor start up?
 
yeah its the motor. you dont think it has anything to do with stackin programers or anything? it didnt really look like much was wrong on compressor nothing obvious anyway..
 
im going to let someone else chime on on this one. im not sure a re flash will help but i bet its worth a try. i will say that i have seen 2 bully dog's wipe 2 separate ECM's and fry one TIPM.

honestly, i have no clue how the AC system ties in so im going to sit and listen.
 
yeah im pretty stumped by it. im surprised no one els has chimed in..
 
sounds like a voltage drop to the PCM, we had a similar problem with a kill switch at the sled pull last night, like everyone said check your wiring harness.
 
Hey this is k-farms buddy, theone having the issuses. i could not find anything wrong with my harness, i will look more though. but it started doing this as soon as i took the banks tuner off. HELP! haha
 
The ac doesn't MECHANICALLY have anything to do with the engine performance other than a horsepower draw to run the compressor. To restate it a different way, there is no reason the compressor should cause a miss in the engine. A couple people have stated they have had wiring issues. You said you checked the harness but did you do a voltage drop test on the wiring from the compressor to the pcm (or junction it plugs into)? An ecm reflash is probably not going to fix your problem because I don't think the ecm has anything to do with the ac compressor. If you don't know how to trace and check wiring either find a friend who knows how, or take it to a reputable shop. (I would avoid a dealership because it seems that dealerships only know how to plug in a computer and follow the instructions given to them by said computer.)
If I were a betting individual, I would put money on there being a short in the ground wire to the compressor.
 
Funny thing the ecm is tied to the Ac system,the high and low pressure sensors send signals to the ecm to control clutch engagement via a relay and also controls the coolant fan to aid in controlling head pressure .
 
FYI sometimes when the AC compressor kicks in only at idle I get a " gas terms here " bad miss for a second, I haven't tracked the problem but I suspect it has to do with the field of the clutch coil causing a voltage spike to the ecm. JMOO
 
Well i did install Flex a lite electronic fans about a weeks before i started having these problems, would that have anything to do with it??? And it started to do the missing the day after i pulled my banks six gun off. It doesnt only do it with the ac on, every so often it will just do it out of nowhere, but ussually when i turn my ac on it is the worst. It also does it when im in the throttle goin down the road and i turn my ac on.
 
diagnosed the problem down to the electronic fans. i believe they sent me a faulty electronic control box.
 
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